Auxiliary section actuator control system and method

ABSTRACT

An auxiliary transmission section (14) shift control system (300)/method is provided which includes control members (246, 328) to prevent auxiliary section synchronized clutch (92, 128) damage if the main transmission section (12) is engaged during an auxiliary section shift. Upon sensing main section engagement during a shift into the auxiliary section high-speed ratio, the force used to engage the high speed ratio is reduced from a first (p*a 224 ) to a considerably lower second (p*(a 224  -a 222 )) level.

BACKGROUND OF THE INVENTION Related Applications

This application is related to copending U.S. patent applications:

Ser. No. 824,673, entitled INTERLOCK MECHANISM FOR RANGE SECTION SLAVEVALVE;

Ser. No. 824,675, entitled RANGE VALVE PRE-EXHAUST;

Ser. No. 824,961, entitled TWO-STAGE RANGE PISTON/CYLINDER ASSEMBLY;

Ser. No. 824,925, entitled VARIABLE PRESSURE RANGE SECTION ACTUATORPISTON;

Ser. No. 824,960, entitled DUAL PRESSURE REGULATOR;

Ser. No. 824,672, entitled VARIABLE PRESSURE RANGE SECTION ACTUATORASSEMBLY;

Ser. No. 824,957, entitled AUXILIARY SECTION ACTUATOR AIR CONTROLSYSTEM;

Ser. No. 824,638 entitled RANGE SECTION ACTUATOR CONTROL SYSTEM ANDMETHOD FOR PREVENTING DAMAGE TO RANGE SECTION SYNCHRONIZERS; and

Ser. No. 824,956, entitled SYNCHRONIZED SPLITTER SECTION PROTECTIONSYSTEM/METHOD;

all assigned to the same assignee, Eaton Corporation, and filed the sameday, Jan. 23, 1992, as this application.

FIELD OF THE INVENTION

The present invention relates to a mechanism and/or method forcontrolling the auxiliary section actuator of a vehicular compoundtransmission. In particular, the present invention relates to mechanismsand/or methods for controlling the engagement of auxiliary sectionsynchronized jaw clutches in compound transmissions of the typecomprising one or more multiple speed auxiliary transmission sectionsconnected in series with a multiple speed main transmission section.More particularly, the present invention relates to a mechanism and/ormethod for protecting the auxiliary section synchronized jaw clutches ofa compound heavy duty vehicular transmission during a compound shift.

DESCRIPTION OF THE PRIOR ART

Compound change gear transmissions of the type having one or moreauxiliary sections connected in series with a main transmission sectionare very well known in the prior art. Such transmissions are typicallyassociated with heavy duty vehicles such as large trucks,tractor/semi-trailers, and the like. Briefly, by utilizing main andauxiliary transmission sections connected in series, assuming properrelative sizing of the ratio steps, the total of available transmissionratios is equal to the product of the main and auxiliary section ratios.By way of example, at least in theory, a compound change geartransmission comprising a four (4) speed main section connected inseries with a three (3) speed auxiliary section will provide twelve(4×3=12) available ratios.

Auxiliary transmission sections are of three general types: range type,splitter type or combined range/splitter type.

In compound transmissions having a range type auxiliary section, therange section ratio step or steps are greater than the total ratiocoverage of the main transmission section and the main section isshifted progressively through its ratios in each range. Examples ofcompound transmissions having range type auxiliary sections may be seenby reference to U.S. Pat. Nos. 4,974,474; 4,964,313, 4,920,815;3,105,395; 2,637,222 and 2,637,221, the disclosures of which are herebyincorporated by reference.

Assignee's well known RT/RTO 11609 and RT/RTO 11610 "Roadranger"transmissions are examples of a "(4+1)×(2)", nine speed and "(5)×(2)"ten speed heavy duty range type transmissions.

In compound transmissions having a splitter type auxiliary section, theratio steps of the splitter auxiliary section are less than the ratiosteps of the main transmission section and each main section ratio issplit, or subdivided, by the splitter section. Examples of compoundchange gear transmissions having splitter type auxiliary sections may beseen by reference to U.S. Pat. Nos. 4,290,515; 3,799,002; 4,440,037 and4,527,447, the disclosures of which are hereby incorporated byreference.

In a combined range and splitter type auxiliary section, or sections,both range and splitter type ratios are provided allowing the mainsection to be progressively shifted through its ratios in at least tworanges and also allowing the main section ratios to be split in at leastone range.

One example of a compound transmission having a single combinedrange/splitter type auxiliary section may be seen by reference to U.S.Pat. Nos. 3,283,613; 3,648,546, the disclosures of which are herebyincorporated by reference. A three gear layer, four-speed combinedsplitter/range type auxiliary section may be seen by reference to U.S.Pat. No. 4,754,665, the disclosure of which is hereby incorporated byreference. Assignee's well known RT/RTO 11613 and RT/RTO 14718 "EatonRoadranger" transmissions are examples of a "(4+1)×(3)" thirteen-speedand a "(4+1)×(4)" eighteen-speed combined range/splitter typetransmission.

Another example is the "Ecosplit" model of transmission sold byZahnradfabrik Friedrichshafen Aktiengeseushaft of Friedrichshafen,Federal Republich of Germany which utilizes a separate splitterauxiliary section in front of, and a separate range auxiliary sectionbehind, the main transmission section.

It should be noted that the terms main and auxiliary sections arerelative and that if the designations of the main and auxiliary sectionsare reversed, the type of auxiliary section (either range or splitter)will also be reversed. In other words, given what is conventionallyconsidered a four-speed main section with two-speed range type auxiliarysection, if the normally designated auxiliary is considered the mainsection, the normally designated main section would be considered afour-speed splitter type auxiliary section therefor. By generallyaccepted transmission industry convention, and as used in thisdescription of the invention, the main transmission section of acompound transmission is that section which contains the largest (or atleast no less) number of forward speed ratios, which allows section of aneutral position, which contains the reverse ratio(s) and/or which isshifted (in manual or semiautomatic transmissions) by manipulation of ashift bar or shift rail or shift shaft/shift finger assembly as opposedto master/slave valve/cylinder arrangements or the like.

In compound transmissions of the range or the combined range/splitter orsplitter/range types, the main transmission section is typically shiftedby means of a shift bar housing assembly, or single shift shaftassembly, controlled by a manually operated shift lever or the like andthe auxiliary range section is shifted, in "repeat H" typetransmissions, by means of button or switch, usually manually operated,which controls a remote slave valve/actuator mechanism. In so-called"double H" or "one and one-half H" type controls, the range is shiftedby switches responsive to positioning of the shift lever. Double H typecontrols are well known in the prior art as may be seen by reference toU.S. Pat. Nos. 4,633,725 and 4,275,612, the disclosures of which areincorporated hereby by reference.

As the range section often utilizes synchronized jaw clutches, toprovide acceptable shift quality and prevent undue wear and/or damage tothe range section synchronized jaw clutches, it has been an object ofthe prior art to provide devices to assure that a range shift beinitiated and hopefully completed while the main transmission section isin neutral.

In view of the above, the prior art compound range type transmissionsusually include a control system, usually a pneumatic control system,including interlock devices, which allowed a range shift to bepreselected by use of a selector button or switch at a master controlvalve but not initiated until the main transmission section is shiftedto, or at least towards, the neutral condition. Such systems typicallyutilized interlocks of the mechanical type on the range section actuatormechanical linkage which physically prevented movement of the rangesection shift fork until the main section shifted into neutral or of thetype wherein the valve (often called the "slave valve") supplyingpressurized air to the range section pistons is either disabled or notprovided with pressurized fluid until a shift to main section neutral issensed, or is only activated and provided with pressurized fluid whilethe main section is shifted to and remains in neutral. Examples of suchtransmissions and the control systems therefor may be seen by referenceto U.S. Pat. Nos. 2,654,268; 3,138,965 and 4,060,005, the disclosures ofwhich are hereby incorporated by reference. Transmissions using rangesection control valves (supply and/or exhaust) which are interlockeduntil a main section shift to neutral occurs may be seen by reference toU.S. Pat. Nos. 3,229,551; 4,450,869; 4,793,378 and 974,474, thedisclosures of which are incorporated by reference.

While the prior art systems do provide considerable protection for therange section synchronizers by preventing initiation of a range shiftuntil the main section is shifted into neutral, they are not totallysatisfactory as while they assure that a range section shift will notinitiate until the main section is in neutral, they do not prevent thecondition wherein the main section shift is faster than (i.e. "beats")the range shift. As is well known, under certain conditions, if therange synchronized clutch attempts to engage while main section isengaged, a portion of the engine torque is transferred to the vehiculardrive wheels entirely by the engaged synchronizer friction surfaces andthe synchronizer friction members can be rapidly damaged. In suchcondition, the range synchronizers, especially the direct or high speedrange synchronizer may be damaged or destroyed relatively quickly. Inthe event of an unintended attempt to make a range only shift, suchdamage may occur within about two (2.0) seconds.

Transmissions utilizing mechanical interlock devices, of both the rigidand the resilient type, may be seen by reference to U.S. Pat. Nos.4,974,474; 4,944,197 and 4,296,642, the disclosures of which are herebyincorporated by reference. Such devices typically locked the rangeclutch into high or low position while the main section is not inneutral and/or locked the main section in neutral if the range clutchwas not engaged in the high or low speed position thereof. While thesesystems will, when operating properly, prevent damage to the rangesynchronizers caused by attempting to engage a range clutch while themain section is not in neutral, they were not totally satisfactory as(i) a fast main section shift can result in the auxiliary section beinglocked in an undesirable ratio, (ii) if a range clutch is hung up on theblocker the main section cannot be engaged to manipulate the clutches,(iii) resilient devices may not properly interlock or may bind, (iv)considerable wear and stress may be caused to the interlock and/or shiftactuator members and/or (v) with wear, friction locks of the interlockmechanisms may occur.

SUMMARY OF THE INVENTION

In accordance with the present invention, the drawbacks of the prior artare minimized or overcome by the provision of an auxiliary sectionactuator control system and method which will protect the auxiliarysection synchronizers if the main section is engaged prior to completionof an attempted auxiliary section shift and which will also allow theattempted auxiliary section shift to be completed upon the jaw clutchmembers of the engaging synchronized clutch achieving a substantiallysynchronous rotation.

The above is accomplished by providing means for sensing if the maintransmission section is in a neutral or not neutral condition, and isresponsive to cause the selected range clutch to be applied with afirst, relatively high force if the main section is in neutral and to beapplied with a second, relatively lower force if the main section is notin neutral.

The invention is particularly well suited for controlling the engagementof the range high speed or direct synchronized clutch. Protection forthe low speed or reduction synchronized auxiliary section clutch isusually not required as when shifting into auxiliary low, torque acrossthe synchronizer friction surfaces will tend, especially in pin typesynchronizers, to cause unblocking of a blocked synchronizer to causerapid engagement of the clutch.

Accordingly, it is an object of the present invention to provide a newand improved auxiliary section (range) shifting control system for acompound transmission of the type utilizing synchronized jaw clutches inthe auxiliary sections thereof.

Another object of the present invention is to provide an auxiliarysection actuator control system/method for urging engagement of aselected auxiliary section synchronized clutch (usually the direct orhigh speed range ratio) with a relatively high force if the maintransmission section is not engaged or with a relatively low force ifthe main transmission section is engaged (not neutral).

These and other objects and advantages of the present invention willbecome apparent from a reading of the detailed description of thepreferred embodiment taken in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a compound transmission having arange type auxiliary section and utilizing the pneumatic control systemof the present invention.

FIG. 1A is a schematic illustration of the shifting mechanisms of thetransmission of FIG. 1.

FIG. 1B is a schematic illustration of the "repeat H" type shift patternof the transmission of FIG. 1.

FIG. 1C is a schematic illustration of a "double H" type shift patternfor the transmission of FIG. 1.

FIG. 2 is a schematic illustration of a compound transmission having acombined splitter/range type auxiliary section with which the pneumaticcontrol system of the present invention is particularly useful.

FIG. 2A is a schematic illustration of the shift pattern for thetransmission of FIG. 2.

FIG. 3 (A and B) is a partial view, in cross-section, of the auxiliarysection 102 of transmission 100.

FIG. 4 is a prospective view of a single shift shaft type shiftingmechanism.

FIG. 5 is a schematic illustration of an air control system forimplementing the present invention.

FIG. 6 is a schematic illustration of an alternative air control system.

FIG. 7 is a schematic illustration of a preferred air control system forimplementing the present invention.

FIG. 8 is a sectional view of a valve assembly for the air controlsystem illustrated in FIG. 7.

FIG. 9 is a section view of the valve assembly of FIG. 8 in a differentoperational position thereof.

FIG. 10 is an exploded view of the valve assembly of FIG. 8.

FIG. 11 is a schematic illustration of an alternate configuration of theair control system illustrated in FIG. 7.

FIGS. 12A-12B are partial sectional views of the alternate valveassembly configuration for the air control system of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Certain terminology will be used in the following description forconvenience in reference only and will not be limiting. The words"upwardly", "downwardly", "rightwardly", and "leftwardly" will designatedirections in the drawings to which reference is made. The words"forward", "rearward", will refer respectively to the front and rearends of the transmission as conventionally mounted in a vehicle, beingrespectfully from left and right sides of the transmission asillustrated in FIG. 1. The words "inwardly" and "outwardly" will referto directions toward and away from, respectively, the geometric centerof the device and designated parts thereof. Said terminology willinclude the words above specifically mentioned, derivatives thereof andwords of similar import.

The term "compound transmission" is used to designate a change speed orchange gear transmission having a multiple forward speed maintransmission section and a multiple speed auxiliary transmission sectionconnected in series whereby the selected gear reduction in the maintransmission section may be compounded by further selected gearreduction in the auxiliary transmission section. "Synchronized clutchassembly" and words of similar import shall designate a positive,jaw-type clutch assembly utilized to nonrotatably couple a selected gearto a shaft by means of a positive clutch in which attempted engagementof said clutch is prevented until the members of the clutch are atsubstantially synchronous rotation and relatively large capacityfriction means are utilized with the clutch members and are sufficient,upon initiation of a clutch engagement, to cause the clutch members andall members rotating therewith to rotate and substantially synchronousspeed.

The terms "neutral" and "not engaged" are used interchangeably and referto a main transmission section condition wherein torque is nottransferred from the transmission input shaft to the mainshaft (intransmissions of the general type illustrated in FIGS. 1 and 2). Theterms "not neutral" and "engaged" are used interchangeably and refer toa main transmission section condition wherein a main section drive ratiois engaged and drive torque is transferred from the transmission inputshaft to the main shaft (in transmissions of the general typeillustrated in FIGS. 1 and 2).

The term "high speed" ratio refers to that ratio of a transmissionsection wherein the rotational speed of the output is greatest for agiven input rotational speed.

Referring to FIGS. 1, 1A and 1B, a range type compound transmission 10is illustrated. Compound transmission 10 comprises a multiple speed maintransmission section 12 connected in series with a range type auxiliarysection 14. Transmission 10 is housed within a housing H and includes aninput shaft 16 driven by a prime mover such as diesel engine E through aselectively disengaged, normally engaged friction master clutch C havingan input or driving portion 18 drivingly connected to the enginecrankshaft 20 and a driven portion 22 rotatably fixed to thetransmission input shaft 16.

In main transmission section 12, the input shaft 16 carries an inputgear 24 for simultaneously driving a plurality of substantiallyidentical countershaft assemblies 26 and 26A at substantially identicalrotational speeds. The two substantially identical countershaftassemblies are provided on diametrically opposite sides of mainshaft 28which is generally coaxially aligned with the input shaft 16. Each ofthe countershaft assemblies comprises a countershaft 30 supported bybearings 32 and 34 in housing H, only a portion of which isschematically illustrated. Each of the countershafts is provided with anidentical grouping of countershaft gears 38, 40, 42, 44, 46 and 48,fixed for rotation therewith. A plurality of mainshaft gears 50, 52, 54,56 and 58 surround the mainshaft 28 and are selectively clutchable, oneat a time, to the mainshaft 28 for rotation therewith by sliding clutchcollars 60, 62 and 64 as is well known in the prior art. Clutch collar60 may also be utilized to clutch input gear 24 to mainshaft 28 toprovide a direct drive relationship between input shaft 16 and mainshaft28.

Typically, clutch collars 60, 62 and 64 are axially positioned by meansof shift forks 60A, 62A and 64A, respectively, associated with the shifthousing assembly 70, as well known in the prior art. Clutch collars 60,62 and 64 may be of the well known synchronized or nonsynchronizeddouble acting jaw clutch type.

Mainshaft gear 58 is the reverse gear and is in continuous meshingengagement with countershaft gears 48 by means of conventionalintermediate idler gears (not shown). It should also be noted that whilemain transmission section 12 does provide five selectable forward speedratios, the lowest forward speed ratio, namely that provided bydrivingly connecting mainshaft drive gear 56 to mainshaft 28, is oftenof such a high gear reduction it has to be considered a low or "creeper"gear which is utilized only for starting of a vehicle under severeconditions and is not usually utilized in the high transmission range.Accordingly, while main transmission section 12 does provide fiveforward speeds, it is usually referred to as a "four plus one" or"(4+1)" main section as only four of the forward speeds are compoundedby the auxiliary range transmission section 14 utilized therewith.

Jaw clutches 60, 62, and 64 are three-position clutches in that they maybe positioned in the centered, nonengaged position as illustrated, or ina fully rightwardly engaged or fully leftwardly engaged position bymeans of a shift lever 72. As is well known, only one of the clutches60, 62 and 64 is engageable at a given time and main section interlockmeans (not shown) are provided to lock the other clutches in the neutralcondition.

Auxiliary transmission range section 14 includes two substantiallyidentical auxiliary countershaft assemblies 74 and 74A, each comprisingan auxiliary countershaft 76 supported by bearings 78 and 80 in housingH and carrying two auxiliary section countershaft gears 82 and 84 forrotation therewith. Auxiliary countershaft gears 82 are constantlymeshed with and support range/output gear 86 which is fixed for rotationwith mainshaft 28 while auxiliary section countershaft gears 84 areconstantly meshed with output gear 88 which surrounds transmissionoutput shaft 90.

A two-position synchronized jaw clutch assembly 92, which is axiallypositioned by means of shift fork 94 and the range section shiftingactuator assembly 96, is provided for clutching either gear 88 to outputshaft 90 for low range operation or gear 86 to output shaft 90 fordirect or high range operation of the compound transmission 10. The"repeat H" type shift pattern for compound range type transmission 10 isschematically illustrated in FIG. 1B. Selection and/or preselection oflow or high range operation of the transmission 10 is by means of anoperator actuated switch or button 98 which is usually located at theshift lever 72.

Although the range type auxiliary section 14 is illustrated as atwo-speed section utilizing spur or helical type gearing, it isunderstood that the present invention is also applicable to range typetransmissions utilizing combined splitter/range type auxiliary sections,having three or more selectable range ratios and/or utilizing planetarytype gearing. Also, as indicated above, any one or more of clutches 60,62 or 64 may be of the synchronized jaw clutch type and transmissionsections 12 and/or 14 may be of the single countershaft type.

The main transmission section 12 is controlled by axial movement of atleast one shift rail or shift shaft contained within the shift barhousing 70 and controlled by operation of the shift lever 72. As isknown, shift lever 72 may be mounted directly to, or remotely from, thetransmission. Devices of this type are well known in the prior art andmay be seen by reference to U.S. Pat. No. 4,621,537, the disclosure ofwhich is hereby incorporated by reference. The range section iscontrolled by operation of button 98, or a position switch 98A in thecase of a "double H" type control, both as well known in the prior art.Shift bar housing 70 may also be of the more conventional multiple shiftrail type, well known in the prior art as may be seen by reference toU.S. Pat. Nos. 4,782,719; 4,738,863; 4,722,237 and 4,614,126, thedisclosures of which are incorporated by reference.

The control system of the present invention is equally applicable tocompound transmissions having range, combined range/splitter orsplitter/range type auxiliary sections.

Referring to FIG. 2, compound change gear mechanical transmission 100 isan eighteen forward speed transmission comprising a main transmissionsection 12A, identical, or substantially identical, to main transmissionsection 12 described above in reference to prior art transmission 10.Main transmission section 12A of transmission 100 differs from maintransmission section 12 of transmission 10 only in that main shaft 28Aextends slightly further into the auxiliary transmission section 102than does main shaft 28 extend into auxiliary transmission section 14.In view of the substantially identical structure of main transmissionsections 12 and 12A, main transmission section 12A will not be describedagain in detail.

Auxiliary transmission section 102 includes two substantially identicalauxiliary countershaft assemblies 104 and 104A, each comprising anauxiliary countershaft 106 supported by bearings 108 and 110 in housingH and carrying three auxiliary section countershaft gears 112, 114 and116 fixed for rotation therewith. Auxiliary countershaft gears 112 areconstantly meshed with and support auxiliary section splitter gear 118which surrounds mainshaft 28A. Auxiliary countershaft gears 114 areconstantly meshed with and support auxiliary section splitter/range gear120 which surrounds the output shaft 122 at the end thereof adjacent thecoaxial end of mainshaft 28A. Auxiliary section countershaft gears 116constantly mesh and support auxiliary section range gear 124, whichsurrounds the output shaft 122. Accordingly, auxiliary sectioncountershaft gears 112 and splitter gear 118 define a first gear layer,auxiliary section countershaft gears 114 and splitter/range gear 120define a second gear layer and auxiliary section countershaft gears 116and range gear 124 define a third layer, or gear group of the combinedsplitter and range type auxiliary transmission section 102.

A sliding two position jaw clutch collar 126 is utilized to selectivelycouple either the splitter gear 118 or the splitter/range gear 120 tothe mainshaft 28A, while a two position synchronized assembly 128 isutilized to selectively couple the splitter/range gear 120 or the rangegear 124 to the output shaft 122. The structure and function of doubleacting sliding jaw clutch collar 126 is substantially identical to thestructure and function of sliding clutch collars 60, 62 and 64 utilizedin connection with transmission 10 while the structure and function ofdouble acting synchronized clutch assembly 128 is substantiallyidentical to the structure and function of synchronized clutch assembly92 utilized in connection with transmission 10. Synchronized clutchassemblies such as assemblies 92 and 128 are well known in the prior artand examples thereof may be seen by reference to U.S. Pat. Nos.4,462,489; 4,125,179 and 2,667,955, the disclosures of all of which areincorporated by reference.

Such clutches typically include a pair of axially engageable jaw clutchmembers, a sensor/blocker device for sensing nonsynchronous rotation ofthe jaw clutch members and blocking axial engagement thereof and a pairof friction surfaces, often conical, which are urged into contact tofrictionally connect the jaw clutch members to cause substantiallysynchronous rotation thereof. During attempted engagement of suchassemblies, assuming a substantial nonsynchronous condition, the clutchwill assume a blocked position wherein the blocker device prevents axialengagement of the jaw clutch members and the friction surfaces areengaged under force. If the clutch assembly remains in the blockedposition under a high axial engagement force while the main transmissionis engaged for an extended period of time, excessive torque loading candamage and/or destroy the friction surfaces.

The detailed structure of the preferred embodiment of auxiliary section102 is illustrated in FIGS. 3A and 3B, wherein it may be seen that therearward end of mainshaft 28A extending into the auxiliary transmissionsection 102 is provided with external splines 130 which mate withinternal splines 132 provided on clutch collar 126 for rotationallycoupling clutch collar 126 to the mainshaft 28A while allowing relativeaxial movement therebetween. The clutch collar 126 is provided withclutch teeth 134 and 136 for selective axial engagement with clutchteeth 138 and 140 provided on gears 118 and 120, respectively. Theclutch collar 126 is also provided with a groove 141 for receipt of ashift fork 142.

Gear 118 surrounds mainshaft 28A and is normally free to rotate relativethereto and is axially retained relative to the mainshaft 28A by meansof retainers 144. Clutch teeth 136 and 138 present tapered surfaces 146and 148 which are inclined at about 35° relative to the axis of themainshaft 28A which provides an advantageous interaction tending toresist nonsynchronous engagement and also tending to cause a synchronousrotation as is described in greater detail in U.S. Pat. No. 3,265,173,the disclosure of which is hereby incorporated by reference. Clutchteeth 136 and 140 are provided with similar complementary taperedsurfaces.

Splitter/range gear 120 is rotatably supported at the inward end 150 ofoutput shaft 122 by means of a pair of thrust bearings while range gear124 surrounds the output shaft 122 and is axially retained thereon bymeans of thrust washers. Located axially between gears 120 and 124, androtationally fixed to output shaft 122 by means of external splines andinternal splines, is the double acting two position synchronized clutchassembly 128. Many of the well known synchronized positive clutchstructures are suitable for use in the auxiliary transmission section ofthe present invention. The synchronized clutch assembly 128 illustratedis of the pin type described in above mentioned U.S. Pat. No. 4,462,489.Briefly, the synchronized clutch assembly 128 includes a slidable jawclutch member 162 axially positioned by a shift fork 164 and carryingclutch teeth 166 and 168, respectively, for axial engagement with clutchteeth 170 and 172, respectively, carried by gears 120 and 124,respectively. Gears 120 and 124 define cone friction surfaces 174 and176, respectively, for frictional synchronizing engagement with matchingfrictional cone surfaces 178 and 180, respectively, carried by thefriction rings 182 and 184, respectively, of the synchronized clutchassembly. Blocker pins 186 and 188 are rotationally fixed to thefriction rings 184 and 182, respectively, and interact with blockeropenings 190 carried by the sliding member 162 to provide the blockingfunction as is well known in the prior art. Synchronizing assembly 128may also include a plurality of spring pins (not shown) for providinginitial engagement of the conical friction surfaces at the initiation ofa clutch engagement operation.

Output shaft 122 is supported by bearings 192 in housing H and extendstherefrom for attachment of a yolk member Y or the like which typicallyforms a portion of a universal joint for driving a propeller shaft to adifferential or the like. The output shaft 122 may also carry aspeedometer gear 194 and/or various sealing elements (not shown).

As may be seen by reference to FIGS. 2 and 3, by selectively axiallypositioning both the splitter clutch 126 and the range clutch 128 in theforward and rearward axial positions thereof, four distinct ratios ofmain shaft rotation to output shaft rotation may be provided.Accordingly, auxiliary transmission section 102 is a 3-layer auxiliarysection of the combined range and splitter type providing fourselectable speeds or drive ratios between the input (countershaft 28A)and output (output shaft 122) thereof. Transmissions of this type arewell known in the prior art and are sold by assignee Eaton Corporationunder the trade names "Super 10" and "Super 18" and may be seen ingreater detail by reference to U.S. Pat. No. 4,754,665, the disclosureof which is incorporated herein by reference.

The shift pattern for the transmission 100 is schematically illustratedin FIG. 2A wherein the "S" arrow indicate a splitter shift and the "R"arrow indicates a range shift.

In the preferred embodiment of the present invention, a single shiftshaft type shifting mechanism 200 of the type illustrated in FIG. 4 isutilized. Mechanisms of this type are known in the prior art as may beseen by reference to U.S. Pat. Nos. 4,920,815 and 4,621,537, thedisclosures of which are incorporated herein by reference.

Briefly, shift lever 98 will interact with block member 202 to causerotational or axial movement of shaft 204 relative to the transmissionhousing. Rotational movement will cause keys, such as key 206 andanother unseen key, to interact with lands or slots provided in the hubsof the shift forks 60A, 62A and 64A to axially fix two of the shiftforks relative to the housing and to axially fix the other shift fork toshaft 204. Axial movement of the shaft 204 and the selected shift forkaxially fixed thereto will then result in engagement and disengagementof the jaw clutches associated therewith.

Accordingly, by monitoring of the axial position of a selected segmentof shift shaft 204, such as one or more neutral detent notches 210, thein neutral-not in neutral condition of the main section 12 oftransmission 10 may be sensed.

The present invention is also applicable to compound transmissionsutilizing the well known multiple parallel rail type shift bar housingassemblies as may be seen by reference to U.S. Pat. Nos. 4,445,393;4,275,612; 4,584,895 and 4,722,237, the disclosures of which are herebyincorporated by reference. Such devices typically include an assemblyextending perpendicular to the shift rails (often associated with ashift rail interlock mechanism) which will assume a first position whenall of the shift rails are in an axially centered neutral position or asecond position when any one of the shift rails is displaced from theaxially centered neutral position thereof.

The present invention is also applicable to compound transmissionswherein other mechanical, electrical, electromagnetic or other types ofsensors are utilized to sense conditions indicative of transmission mainsection neutral (not engaged) or not neutral (engaged) conditions.

Although the auxiliary transmission sections are typically attached tothe main transmission section, the term "auxiliary transmission section"as used herein is also applicable to detached drive train devices suchas multiple-speed axles, multiple-speed transfer cases and the like.

While the present invention is equally applicable to transmission 10illustrated in FIG. 1 and transmission 100 illustrated in FIGS. 2 and 3,as well as other compound transmissions utilizing synchronized auxiliarysection jaw clutch assemblies, for purposes of simplification and easeof understanding, the present invention will be described primarily asutilized with the compound range type transmission illustrated in FIGS.1, 1A, 1B and 1C.

Assuming a shift control of the type illustrated in FIG. 1B, i.e. a"repeat H" type control, a 4th-to-5-th speed compound shift involvesdisengaging jaw clutch 60 from 4th/8th speed input gear 24, thendisengaging clutch 92 from range low speed or reduction gear 86 andengaging clutch 92 with the high speed or direct range gear 88 and thenengaging jaw clutch 62 with 1st/5th speed main section gear 54. Toaccomplish this, the vehicle operator will preselect "HI" with the rangeselector button 98, will shift from the 4/8 position to N and then tothe 1/5 position with shift lever 72. In prior art range typetransmissions, such as the 9-speed RT/RTO 11609 "Roadranger"transmission manufactured and sold by Eaton Corporation, a two-positionslave valve having a first position for causing "HI" range to beselected and a second position for causing "LO" range to be selected wasinterlocked in one of its two positions by a plunger or the likewherever the main transmission section 10 was not in neutral. Examplesof such valves and interlocks may be seen by reference toabove-mentioned U.S. Pat. Nos. 3,229,551; 4,450,869; 4,793,378 and4,974,474.

As indicated previously, while these devices will, under mostconditions, protect the range section synchronizers by preventinginitiation of a range shift until the main section is shifted intoneutral, under certain conditions the main section shift may completeprior to the range shift which will place the range synchronizer atrisk. This is a considerably greater problem for range upshifts(4th-to-5th) than for range downshifts (5th-to-4th) as torque across thesynchronizer friction cone surfaces (174/178 in FIG. 3A) when engagingdirect range gear 88 will tend to increase the tendency of thesynchronizer being hung up on the synchronizer blockers while torqueacross the friction cone surfaces (176/180 in FIG. 3B) when engagingreduction range gear 86 will tend to pull the synchronizer to anunblocked condition. Generally, in transmissions of the type illustratedin FIGS. 1 and 2, range section synchronizer burn-out is not seen as asignificant problem in range section downshifts.

Referring to the transmission of FIG. 1, another serious problem mayoccur when a driver in 4th gear decides to upshift, the preselects arange upshift and then moves the shift lever to or towards the neutralposition. If the driver quickly changes his mind and moves the shiftlever back to the 4/8 position without changing the range selection, therange clutch may attempt top complete a range only 4-8 upshift and thelarge speed differential across the synchronizer cone friction surfacesmay result in rapid damage thereto. In such situations, a synchronizermay be severely damaged or destroyed with two seconds.

Similar inadvertent attempted compound skip upshifts will have similarresults. For another example, if a drive inadvertently preselects orforgets a preselection of a range upshift, and then attempts a 4-3downshift, the actual result will be an attempted 4-7 upshift with alarge speed differential across the synchronizer friction surfaces.

The auxiliary section control system/method of the present inventionovercomes the prior art drawbacks by reducing the force applied by shiftfork 94 to engage high speed range gear 86 to a relatively low levelwhen a main section not neutral condition is sensed. The relatively lowforce is selected to be sufficient to cause the synchronized clutch toengage when synchronous conditions occur but low enough to assure thatthe risk of synchronizer burn out is minimized or eliminated.

While the present invention is particularly well suited for use incontrolling the engagement of a synchronized range clutch, especiallythe high speed or direct range clutch of a compound transmission, it isnot intended to be limited to such use and could be useful incontrolling the engagement of synchronized splitter clutches or thelike.

For purposes of simplification, the present invention will be describedin connection with its expected most advantageous use, namelycontrolling the force applied to engage the direct or high speedsynchronized range clutch (clutch teeth 166 and 170 in FIG. 3A) of arange (10), range/splitter or splitter/range (100) type of compoundtransmission.

While the typical force applied to engage a range clutch is a functionof the effective fluid pressure (usually pneumatic) applied to aneffective piston area, engagement force may also be applied byelectromechanical means such as electric motor driven ball screws or thelike, electromagnetic means such as solenoid type devices, or otherforce application means. With fluid pressure application systems, theapplication force applied to a range clutch is variable by varying theeffective fluid pressure and/or effective piston area. Withelectromagnetic and electromechanical systems, force may be varied byvarying the electric current, voltage or the like.

While not intending to so limit the present invention, the presentinvention will be described in its preferred mode of a pneumaticactuation system.

In the prior art range clutch actuators, assuming a range shift has beenselected/preselected, the main transmission section has been shiftedinto neutral and the range valve interlock is released, the range valvewill provide the selected chamber of the range clutch actuationcylinder/piston with a pressure (usually regulated to about 60 psi-to-80psi) sufficient to apply a force of about (300 to 400 lbs). To quicklymove the selected clutch into engagement and/or into the blockedposition and to apply a significant synchronizing force through thesynchronizer friction cones to cause rapid synchronous rotation of theclutch members, unblocking of the synchronizer and movement of theclutch members through the blocker and into positive engagement. If themain section remains in neutral, or in the event of a range sectionshift into the range low-speed or reduction ratio, the force will notresult in damage to the synchronizer and will result in a relativelyquick range section engagement. However, in the event the main sectionis engaged prior to completion of an attempted range section upshiftinto the range section high speed or direct ratio, serious damage toand/or destruction of the synchronizer may occur relatively quickly, inthe event of an attempted skip upshift usually within about two (2.0)seconds.

It has been discovered that, upon sensing conditions indicative of amain section shift into engagement (i.e. not neutral) prior tocompletion of an attempted range section shift into the range sectionhigh speed or direct ratio, if the force applied to engage the directrange clutch is reduced to a relatively lower section level (about 40 to80 lbs.) the direct ratio synchronized range clutch will still engageupon a substantially synchronous rotation of the clutch members (sleeve162 and gear 114 in FIG. 3A) while the synchronizers will not, at leastwithin a predetermined time (such as 20 to 45 seconds), be damaged ordestroyed.

The second lower force is not acceptable for normal engagement of therange synchronizer clutches as a sufficient force is not applied to thesynchronizer friction clutches and many range shifts would take anobjectionably long period of time.

While a variable pressure pressure-regulator may be used to achieve asecond force level for applying the direct range clutch, in thepreferred embodiments a differential area piston method is utilized. Asmay be seen by reference to FIGS. 5, 6 and 7, the range clutch actuatorpiston assembly 220 defines a differential area piston 221 having afirst surface area 222 (about 3.96 sq. inches) pressurized to engage thelow range clutch, and a second larger surface area 224 (about 4.65 sq.inches) pressurized to engage to high range clutch with the first levelof force (p*a₂₂₄ equalling about 371 lbs.). Pressurizing both thesurface areas will result in regulated pressure (80 psi) applied to thedifferential area (the second surface area 224 minus the first surfacearea 222) and is effective to apply the direct clutch with a relativelylow second level of force (p*(a₂₂₄ -a₂₂₂) equaling about 54 lbs.)

Piston 221 is sealingly and slidably received in a cylinder divided intotwo chambers 222A and 224A. Piston 221 includes a shaft 226 to which ismounted shift yoke 164 for shifting synchronized clutch 128 or 92 to theselected positions thereof.

To provide the synchronizer protection effect, while still urging thedirect range clutch into engagement, the present invention is effectiveto (i) pressurize only the second surface area 224 when a range shiftinto direct is selected and the main section is in neutral and (ii) topressurize both the first and the second surface areas (222 and 224)when a range section shift into direct is selected and the main sectionis engaged in a ratio (i.e. not neutral).

The second force level must be sufficient to cause a direct range clutchengagement when synchronous or substantial synchronous rotation of thehigh speed range clutch clutch members is achieved and preferably shouldbe sufficient to maintain the direct range in engagement (or in-geardetent means should be provided). The second force should besufficiently low so that when the synchronizer is engaged on the block,with the main transmission section engaged, the synchronizer coneclutches or the like will not suffer substantial damage for apredetermined period of time, such as, for example, twenty (20) toforth-five (45) seconds.

As an example, a first force of about 300 to 400 lbs. with a secondforce of about 40 to 80 lbs. has proven highly satisfactory.

Schematics of air systems to achieve the above effect may be seen byreference to FIGS. 5, 6 and 7 while a valve assembly particularly wellsuited to achieve the above may be seen by reference to FIGS. 8, 9 and10.

As indicated previously, the not engaged (neutral) and the engaged (notneutral) conditions of the main section (12) of transmission (10) may besensed by sensing axially nondisplaced or displaced positions of themain transmission section shift shaft(s) 204. Such axial displacement ofa shift shaft or shift rail may be sensed on the shaft or rail per se,on an extension thereof, or on a cross-shaft or the like.

Devices for applying either a first or a second relatively lesser forceto shifting forks, such as engaging with a larger first and disengagingwith a second smaller force, are known in the prior art as may be seenby reference to U.S. Pat. No. 4,928,544, the disclosure of which ishereby incorporated by reference.

A synchronizer protecting range shift air control system 230 isillustrated in FIG. 5. The master range valve 232 is connected to asource of filtered and regulated air from filter regulator 234. Inheavy-duty vehicles, the regulated air pressure is usually 60 to 80 psi.Switch or lever 98 is effective to either pressurize (Low) or vent(High) the low Pressure signal or pilot line 236. The low range pilotline 236 connects to the range slave valve 238 which is a two-position,four-way valve spring 240 biased to the high range position (i.e.chamber 224A pressurized and chamber 222A exhausted) and responsive topressurization of pilot line 236 to move to the low range position (i.e.chamber 222A pressurized and chamber 224A exhausted).

A shaft 242 movable to either an in-gear position or a neutral positionis provided with an interlock plunger 244 for preventing initialmovement of slave valve 238 until the main section is shifted into aneutral position. All of the above-described components of controlsystem 230 are considered to be relatively standard in prior art rangetype transmissions.

To the above components is added a two-position, three-way rangeprotection valve 246. Range protection valve 246 is constantly connectedvia line 248 to source pressure and to the outlet port 250 of the slavevalve associated with the low range chamber 222A. Range protection valve246 includes a plunger 252 for sensing the in-gear or neutral conditionsof the main section. The outlet port 253 of valve 246 connects to lowrange chamber 222A of the range actuator piston assembly 220.

When the main section is in neutral, as shown in FIG. 5, the outlet port250 of the slave valve 238 is connected directly through the rangeprotection valve 246 to chamber 222A. When the main section is engaged,the range protection valve 246 connects low range chamber 222A tosource, regardless of the position of the slave valve 238.

Accordingly, if at any time after initiation of a range shift the maintransmission section is shifted into an engaged (not neutral) condition,then the low range chamber 222A will be pressurized, regardless of theposition of the slave valve 238. This will allow normal completion of ashift into range low or a shift into range high at a considerablyreduced second force.

A similar control system 270 is illustrated in FIG. 6. System 270differs from system 230 described above primarily in that a shaft 272,which interacts with groove 210 in single shift shaft 204, provides amechanical actuation for the range protection valve 246 and alsoactuates an air rather than a mechanical interlock mechanism, interlockvalve 274. Briefly, two-position, two-way interlock valve 274 willprevent pressurizing or exhausting of low pilot line 236 at the slavevalve 238 until the transmission main section is shifted into neutral.

As in system 230, range protection valve 246 will pressurize the lowrange chamber 222A when the main transmission section is engaged (notneutral) regardless of the positions of the other valve members. Thus,when low is selected, and the main section is shifted to neutral, thehigh range chambers 224A of the piston assembly 220 is exhausted andthen, when a shift into main section engaged occurs, the low pressurechamber 222A will be pressurized to complete the range downshift.

Alternatively, valve 246 could be biased rightwardly by spring 273 andsystem 270 would function substantially identically to system 230described above.

Components of systems 230, 270 and 300 (to be described below) havingsubstantially identical structure and function have been assigned likereference numerals.

The air control system 300 is schematically illustrated in FIG. 7. Thecontrol system 300 includes a master valve 301 similar to master valve232 described above and having a selector switch 98 for selecting high(HI) or low (LO) range ratio. The master valve 301 may also include asecond selector switch 302 for selecting either splitter high orsplitter low splitter ratio. A splitter low pilot line 304 controls theoperation of a two-position three-way splitter slave valve 306. Mastervalves such as 301 are associated with compound transmissions of thecombined range and splitter type as illustrated in FIGS. 2 and 3.

The range slave valve assembly 310 includes a three-position, four-wayvalve 312 and a latch and override mechanism 314. Valve 312 has port 316connected to exhaust, a port 318 connected to source air from thefilter/regulator 234 (80 psi), a port 320 connected to the high rangecylinder 224A of the differential area piston assembly 220, and a port322 connected to the low range cylinder 222A of the differential areapiston assembly 220.

Valve 312 has a first 324 position (upper position in FIG. 7), forselecting high range, wherein the high range cylinder 224A is connectedto source pressure and the low range cylinder 222A is vented to exhaust.Valve 312 has a second 326 position (lower position in FIG. 7), forselecting low range, wherein the low range cylinder 222A is connected tosource pressure and the high range cylinder 224A is vented to exhaust.Valve 312 has an intermediate or third 328 position wherein both thehigh (224A) and the low (222A) range cylinders are connected to thesource pressure.

The valve 312 is spring 330 biased into the first (324) or high speedrange position and may be moved to its second (326) or low speed rangeposition by action of low range pilot pressure from line 236. Bymechanical means of an override actuator lever or link 332 interactingwith the notches 210 and adjacent lands on shift shaft 204, the valve ismovable from the first (324) position to the intermediate third (328)position thereof if the main transmission is shifted to an engagedposition while the valve is in the first position thereof.

The latch function of the latch and override assembly 314 is to preventthe valve from moving from the first 324 to the second 326, or from thesecond 326 to the first 324, positions thereof when the main section isin neutral but not to prevent movement of the valve from the first 324to the intermediate 328 third positions thereof. The latch and overrideassembly thus provides the range interlock function of preventinginitiation of a range shift until the main section is shifted intoneutral. A specific structure for the valve 312 and the latch andactuator assemblies 314 is illustrated in FIGS. 8, 9 and 10 anddescribed in greater detail below.

As an alternative design, see FIGS. 11 and 12, the low range pilot line236 may be omitted and a modified or additional actuator lever 355 andshift shaft 204 utilized to mechanically shift the valve 312 against thebias of spring 330 into the second 326 low range position thereof inresponse to shifting into the low range portion of a "double H" typeshift pattern. The alternative design is discussed below and more fullyillustrated in FIGS. 11, 12A and 12B.

In operation, for a shift from high to low range ratio, the selector 98will be moved to select/preselect the "LO" position and pilot line 236will be pressurized. As soon as the shift shaft position indicates themain section is in neutral, the latch 314 will release allowing thevalve mechanism 312 to assume the second position 326 thereof which willcause pressurizing of low range chamber 222A and exhaust of high rangechamber 224A. The override does not effect the valve in the secondposition 326 thereof, and thus the positioning of valve 312 will remainas is until selector 98 is moved.

To shift from low to high range ratio, the selector 98 will be moved toselect/preselect the "HI" position and the pilot line 236 will beexhausted. As soon as the shift shaft position indicates a maintransmission neutral condition, the latch is released and the valve 312will move to the first 324 position thereof under the bias of spring330. High range chamber 224A will be pressurized and low range chamber222A will be exhausted. Thereafter, as the transmission main section isengaged, the actuator link 332 will move the valve 312 from the firstposition (324) to the third or intermediate position (328) wherein boththe high range ratio (224A) and low range ratio (222A) cylinder chambersare pressurized to provide a reduced force on the shift fork, 94 or 164,urging the high speed range synchronized clutch into engagement.

The structure of the range slave valve assembly is illustrated in FIGS.8, 9 and 10. Range slave valve assembly 310 is contained within atwo-piece housing 340 defining a spool housing portion 342 and a latchand override mechanism portion 344. Valve spool portion 342 defines aninternal bore 346 in which is received a valve spool 348 and alsodefines ports 316 (two), 318, 320 and 322 connected to exhaust, supply,the low range piston chamber 222A and the high range piston chambers224A, respectively. A port 350 for connection to the low speed pilotline 236 is defined in the latch and override portion. The leftward endof valve spool is provided with a piston surface 352 sealingly andslidably received in a chamber 354 communicating with port 350. Biasingspring 330 is seated at the rightward end of bore 346 and engages theend of valve spool 348 to urge the valve spool leftwardly.

The first position 324 of valve 312 corresponds to the most leftwardlyposition of valve spool 348 as seen in the upper half of FIG. 8. In thisposition, ports 318 and 322 are in fluid communication, ports 320 andthe left port 316 are in fluid communication, and the right port 316 issealed from the other ports.

The second position 326 of valve 312 corresponds to the rightwardlyposition of valve spool 348 as illustrated in FIG. 9. In this position,ports 318 and 320 are in fluid communication, ports 322 and righthandport 316 are in fluid communication and the left hand port 316 is sealedfrom the other ports. As illustrated in the left upper and lowerportions of FIG. 9, spool 348 may be urged to the rightward or secondposition either by pressurizing the chamber 352 through port 350 and lowrange pilot line 236 (FIG. 9) or by means of a lever or link 355 similarto lever 332 but acting on large diameter surface of a shaft utilized ina double H shift pattern and push rod portion 356 of spool 348 (FIGS.12A and 12B).

The third or intermediate position 328 of valve 312 is illustrated inthe lower portion of FIG. 8. In this position, both ports 320 and 322fluidly communicate with source port 318 and both exhaust ports aresealed from the other ports. As may be seen by reference to FIG. 8, whenlever actuator 332 rides on the outer surface of shaft 204, the leverwill engage a portion of push rod 356 to urge the spool to theintermediate position thereof. It is noted, that when the spool is inthe rightward most position, i.e., the second position 326 of valve 312,the override lever 332 (see FIG. 8) will not effect the position of thespool.

The latch function of the latch and override assembly 314, is providingthe range interlock function of preventing initiation of a range shiftuntil the main transmission section is shifted into neutral, and isaccomplished by collet 360, detent roller 362 and grooves 364 and 366 inthe push rod extension 356 of the valve spool. Detents 362 are receivedin slots in housing portion 344 for radial movement and the outersurface of push rod extension 356 includes a first detent groove 364which will align with the detent rollers when the spool is in the secondposition thereof (FIG. 9) and a second detent groove 366 which iselongated and will align with the detents when the spool is in eitherthe first position or in the second position or is in transittherebetween. When the collet 360 is in the retracted position under thebias of spring 368, see the top of FIG. 8 and FIG. 9, the detents ballsor rollers 362 are movable radially outwardly and will not effect theaxial movement of the valve spool 348. However, when the collet ispushed rightwardly by the lever 332, see the bottom of FIG. 8, thedetent rollers 362 are locked against axially outward movement and thespool 348 is interlocked in either the first to the intermediate (third)axial Position or in the second axial position thereof.

An "exploded" view of the range valve assembly 310 may be seen byreference to FIG. 10. For purposes of clarity, the various seals,gaskets and the like are not identified by reference numerals.

An alternate configuration of the air control system 300 and range valveassembly 310 illustrated in FIGS. 7-10 may be seen by reference to FIGS.11, 12A and 12B.

FIGS. 11, 12A and 12B illustrate an air control system 400 for use witha "double H" shift mechanism wherein switch 98A is not utilized but ashift shaft 204A, is provided with relatively smaller diameter portions402 and relatively larger diameter portions 404, respectively,corresponding to operation in the high range or low range portion,respectively, of the "double H" pattern. Master valve 406 differs fromthe master valve 301 in that only a splitter selector switch or button302 is provided.

The valving portion 312 of valve assembly 408 is identical with thevalving portion 312 of valve assembly 310. The actuator portion 410 ofvalve assembly 408 differs considerably from the latch and overrideportion 314 of valve assembly 310.

In addition to the link member 332 which cooperates with neutral notch210 to move the valving portion 312 from the first 324 to the thirdposition 328 thereof upon sensing a main section engaged condition, asecond, independent, link or lever 412 is provided. Lever 412 is thehigh/low range actuator and cooperates with raised surfaces 404 on shiftshaft 204A to move valve portion 312 to the second position 326 thereofas shift shaft 204A is rotated into the high range portion of the"double H" pattern.

As may be seen by reference to FIGS. 12A and 12B, lever 412 replaces thepiston assembly 352/354 utilized in valve assembly 310 and thus the lowrange pilot port 350 is sealed with a plug 414.

FIG. 12A shows valve assembly 410 in the high speed range position andFIG. 12B illustrates valve assembly 410 is the low speed range positionthereof. While collette 360 is utilized, the detent rollers are notneeded as the latch function is unnecessary due to the fact thatelimination of a range selector switch also eliminates the possibilityof preselection of a range shift.

While the present invention has been described with a certain degree ofparticularity, it is understood that the present description is by wayof example only and that modification and rearrangement of the parts ispossible within the spirit and the scope of the present invention ashereinafter claimed.

I claim:
 1. A control method for controlling a shift actuator (96)associated with a synchronized jaw clutch (92) for selectively engagingand disengaging a selectable ratio in a first transmission section (14)of a compound transmission (10) comprising first and second (12)multiple speed sections connected in series, said method comprising:(a)sensing selection of engagement of said first transmission sectionselectable ratio; (b) sensing if the second transmission section is ineither an engaged or a nonengaged condition; (c) responding to sensing(i) a selection of engagement of said first transmission sectionselectable ratio and (ii) said second transmission section not engagedby causing said actuator to urge said synchronized jaw clutch intoengagement with a first force (p * a₂₂₄); and (d) responding to sensing(i) a selection of engagement of said first transmission sectionselectable ratio and (ii) said second transmission section engaged bycausing said actuator to urge said synchronized jaw into engagement witha second force (p * (a₂₂₄ -a₂₂₂), said second force being smaller thansaid first force.
 2. The method of claim 1 wherein said first force isat least twice as large as said second force.
 3. The method of claims 1or 2 wherein said compound transmission is a manually operated rangetype transmission, said first transmission section is an auxiliary rangesection having a high speed and a low speed ratio and said selectableratio is the high speed range section ratio.
 4. The method of claims 1or 2 further comprising:(e) prohibiting initiation of engagement of saidselectable ratio until said second transmission section is sensed as notengaged at the time of or after a selection of engagement of saidselectable ratio.
 5. The method of claim 3 further comprising:(e)prohibiting initiation of engagement of said selectable ratio until saidsecond transmission section is sensed as not engaged at the time of orafter a selection of engagement of said selectable ratio.
 6. A methodfor controlling the shifting of a compound change gear transmission (10)of the type comprising a manually shifted multiple-speed maintransmission section (12) shiftable into an engaged or a not engagedcondition connected in series with a multiple-speed auxiliary section(14), said auxiliary section including low-speed (168/172) andhigh-speed (166/170) synchronized jaw clutches (92) shiftable by anactuator (96) to engage either a low-speed or a high speed auxiliarysection ratios, respectively, in response to selection by a masterselector (98/98A/412, 402 and 404), said method characterized by:sensinga selection of a shift of said auxiliary section into a selected one ofthe low-speed and the high-speed auxiliary section ratios; sensing saidmain transmission section being in either an engaged or in a not engagedcondition thereof, responding to sensing (i) a selection of a shift intothe auxiliary section high-speed ratio and (ii) said main transmissionsection in the not engaged condition by causing said actuator to urgesaid auxiliary section high speed synchronized jaw clutches intoengagement with a first force level; and thereafter responding to (i) acontinuing selection of a shift into auxiliary section high-speed ratioand (ii) said main transmission section in an engaged condition bycausing said actuator to urge said auxiliary section high speedsynchronized jaw clutches into engagement with a second force level,said second force level being considerably lower than said first forcelevel.
 7. The method of claim 6 further comprising:responding to sensing(i) a selection of a shift into the auxiliary section low-speed ratioand (ii) said main transmission section in the not engaged condition, bycausing said actuator to urge said auxiliary section low-speedsynchronized clutches into engagement with a third force levelsubstantially equal to said first force level; and thereafter,responding to about 80% to 85% of a continuing selection of a shift intothe auxiliary section low-speed ratio by causing said actuator to urgesaid auxiliary section low-speed synchronized clutch into engagementwith said third force level regardless of the engaged or not engagedcondition of said main transmission section.
 8. The method of claims 6or 7 wherein said auxiliary section (14) is a two-speed range sectionand said high speed ratio is a direct speed ratio.
 9. The method ofclaims 6 or 7 further comprising prohibiting initiation of a selectedauxiliary section shift until main transmission section in neutral issensed.
 10. The method of claim 8 further comprising prohibitinginitiation of a selected auxiliary section shift until main transmissionsection in neutral is sensed.
 11. The method of claims 6 or 7 whereinsaid first force level is at least twice as large as said second forcelevel.
 12. The method of claim 8 wherein said first force level is atleast twice as large as said second force level.
 13. The method of claim9 wherein said first force level is at least twice as large as saidsecond force level.
 14. The method of claim 10 wherein said first forcelevel is at least twice as large as said second force level.
 15. Themethod of claims 6 or 7 wherein said high-speed auxiliary synchronizerclutch is a pin type synchronizer.
 16. The method of claim 8 whereinsaid high-speed auxiliary synchronizer clutch is a pin typesynchronizer.
 17. The method of claim 7 wherein said first force issubstantially equal to the sum of said second and third forces.
 18. Amethod for controlling a shift actuator (220) an auxiliary transmissionsection (14) of a compound transmission (10) including a maintransmission section (12) having engaged and not engaged positionsconnected in series with said auxiliary transmission section, saidauxiliary transmission section including a selectable high-speed ratioand a selectable low-speed ratio each of said auxiliary section ratiosengageable by a synchronized jaw clutch assembly (92/128), switch means(98/98A/412) for selecting a desired auxiliary section ratio, saidactuator (220) comprising a first force application means (224) forapply a first force in a first axial direction to said synchronizedclutch assembly and a second force applications means (222) for applyinga second force in a second axial direction opposite said first axialdirection to said synchronized clutch assembly, said first force largerthan said second force, force in said first axial direction effective tourge said synchronized clutch assembly to engage said high speed ratioand force in said second axial direction effective to urge saidsynchronized clutch assembly to engage said low speed ratio, said methodcomprising:sensing the current engaged or not engaged position of saidmain transmission section, and applying said second force whenever saidmain transmission section is in the engaged position thereof (324/328).19. The method of claim 17 further comprising:applying said first forceand not applying said second force when said main transmission sectionis in the not engaged position thereof and the high-speed ratio has beenselected.
 20. The method of claim 19 further comprising:applying boththe first and second forces when high-speed ratio is selected and saidmain transmission section is in the engaged position thereof after aninitial application of said first force without application of saidsecond force.
 21. The control method of claims 18 or 19 furthercomprising applying said second force and not applying said first forcewhen low-speed ratio is selected.
 22. The control method of claim 20further comprising applying said second force and not applying saidfirst force when low-speed ratio is selected.
 23. The control method ofclaims 18 or 19 further comprising:applying said second force and notapplying said first force when said low-speed ratio is selected and saidmain transmission section has been in the not engaged position after theselection of the low-speed ratio.
 24. The control method of claim 20further comprising:applying said second force and not applying saidfirst force when low-speed ratio is selected and said main transmissionsection has been in the not engaged position after the selection of thelow-speed ratio.
 25. The method of claim 18 or 19 wherein said firstforce is at least 10% larger than said second force.
 26. The method ofclaim 20 wherein said first force is at least 10% larger than saidsecond force.
 27. A control system for controlling a shift actuator (96)associated with a synchronized jaw clutch (92) for selectively engagingand disengaging a selectable ratio in a first transmission section (14)of a compound transmission (10) comprising first and second (12)multiple speed sections connected in series, said second sectionshiftable into engaged and not engaged conditions, said systemcomprising:(a) means for sensing selection of engagement of said firsttransmission section selectable ratio (98/236); (b) means for sensing ifthe second transmission section is in either an engaged or a not engagedcondition (204/210/332); (c) means (324) for responding to sensing (i) aselection of engagement of said first transmission section selectableratio and (ii) said second transmission section not engaged by causingsaid actuator to urge said synchronized jaw clutch into engagement witha first force; and (d) means (328) for responding to sensing (i) aselection of engagement of said first transmission section selectableratio and (ii) said second transmission section engaged by causing saidactuator to urge said synchronized jaw into engagement with a secondforce, said second force being smaller than said first force.
 28. Thesystem of claim 27 wherein said first force is at least 10% larger thansaid second force.
 29. The system of claims 27 or 28 wherein saidcompound transmission is a manually operated range type transmission,said first transmission section is an auxiliary range section having ahigh speed and a low speed ratio and said selectable ratio is the highspeed range section ratio.
 30. The system of claims 27 or 28 furthercomprising:(e) means (244/274/314) for prohibiting initiation ofengagement of said selectable ratio until said second transmissionsection is sensed as not engaged after a selection of engagement of saidratio.
 31. The system of claim 29 further comprising:(e) means(244/274/314) for prohibiting initiation of engagement of saidhigh-speed ratio until said second transmission section is sensed as notengaged after a selection of engagement of said ratio.
 32. The system ofclaims 27 or 28 wherein said auxiliary section (14) is a two-speed rangesection and said high speed ratio is a direct speed ratio.
 33. Thesystem of claims 27 or 28 further comprising means (244/274/314) forprohibiting initiation of a selected auxiliary section shift until maintransmission section in neutral is sensed.
 34. The system of claim 29further comprising prohibiting initiation of a selected auxiliarysection shift until main transmission section in neutral is sensed. 35.The system of claims 27 or 28 wherein said first force level is at leasttwice as large as said second force level.
 36. The system of claim 20wherein said first force level is at least twice as large as said secondforce level.
 37. The system of claim 30 wherein said first force levelis at least twice as large as said second force level.
 38. The system ofclaim 31 wherein said first force level is at least twice as large assaid second force level.
 39. The system as claims 27 or 28 wherein saidhigh-speed auxiliary synchronizer clutch is a pin type synchronizer. 40.A system for controlling the shifting of a compound change geartransmission (10) of the type comprising a manually shiftedmultiple-speed main transmission section (12) shiftable into an engagedor a not engaged condition connected in series with a multiple-speedauxiliary section (14), said auxiliary section including high-speed(168/172) and low-speed (166/170) synchronized jaw clutches (92)shiftable by an actuator (96) to engage either a low-speed or a highspeed (direct) auxiliary section ratio in response to selection by amaster selector (98/98A/412), said system characterized by:means (98)for sensing a selection of a shift of said auxiliary section into aselected one of the low-speed and the high-speed auxiliary sectionratios; means (204/310/332) for sensing said main transmission sectionbeing in either an engaged or in a not engaged condition thereof, means(324) for responding to sensing (i) a selection of a shift into theauxiliary section high-speed ratio and (ii) said main transmissionsection in the not engaged condition by causing said actuator to urgesaid auxiliary section high speed synchronized jaw clutches intoengagement with a first force level; and means (328) for thereafterresponding to (i) a continuing selection of a shift into auxiliarysection high-speed ratio and (ii) said main transmission section in anengaged condition by causing said actuator to urge said auxiliarysection high speed synchronized jaw clutches into engagement with asecond force level, said second force level being lower than said firstforce level.
 41. The system of claim 40 further comprising:means (326)for responding to sensing (i) a selection of a shift into the auxiliarysection low-speed ratio and (ii) said main transmission section in thenot engaged condition, by causing said actuator to urge said auxiliarysection low-speed synchronized clutches into engagement with a thirdforce level substantially equal to about 80% to 85% of said first forcelevel; and thereafter, responding to a continuing selection of a shiftinto the auxiliary section low-speed ratio by causing said actuator tourge said auxiliary section low-speed synchronized clutch intoengagement with said third force level.
 42. A system for controlling ashift actuator (220) for an auxiliary transmission section (14) of acompound transmission (10) including a main transmission section (12)having engaged and not engaged positions connected in series with saidauxiliary transmission section, said auxiliary transmission sectionincluding a selectable high-speed ratio and a selectable low-speed ratioeach of said auxiliary section ratios engageable by a synchronized jawclutch assembly (92/128), switch means (98/98A/412) for selecting adesired auxiliary section ratio, said actuator (220) comprising a firstforce application means (224) for apply a first force in a first axialdirection to said synchronized clutch assembly and a second forceapplications means (222) for applying a second force in a second axialdirection opposite said first axial direction to said synchronizedclutch assembly, said first force larger than said second force, forcein said first axial direction effective to urge said synchronized clutchassembly to engage said high speed ratio and force in said second axialdirection effective to urge said synchronized clutch assembly to engagesaid low speed ration, said system comprising:means (204/210/332) forsensing the current engaged or not engaged position of said maintransmission section, means (324) for applying said first force and notapplying said second force when said transmission section is in the notengaged position thereof and the high-speed ratio has been selected, andmeans (324) for applying said second force whenever said maintransmission section is in the engaged position thereof (324/328). 43.The system of claim 42 further comprising:means (328) for applying boththe first and second forces when high-speed ratio is selected and saidmain transmission section is in the engaged position thereof after aninitial application of said first force without application of saidsecond force.
 44. The control system of claim 42 further comprisingmeans (326) for applying said second force and not applying said firstforce when low-speed ratio is selected.
 45. The control system of claim43 further comprising means (326) for applying said second force and notapplying said first force when low-speed ratio is selected.
 46. Thecontrol system of claim 42 further comprising:means (326) for applyingsaid second force and not applying said first force when said low-speedratio is selected and said main transmission section has been in the notengaged position after the selection of the low-speed ratio.
 47. Thecontrol system of claim 43 further comprising:means (326) for applyingsaid second force and not applying said first force when low-speed ratiois selected and said main transmission section has been in the notengaged position after the selection of the low-speed ratio.
 48. Thesystem of claim 42 or 46 wherein said first force is at least 10% largerthan said second force.
 49. The system of claims 43 wherein said firstforce is at least 10% larger than said second force.